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Too light?
- Thread starter JCSO62
- Start date
Welcome to the forum.
Yes, the bullet is likely too light and is going too fast for that rifling pitch or twist. A 14" pitch is much more appropriate for most bullets in that weight range. Bullets have to have a minimum amount of spin to be stable, and the longer the bullet and the lower its density, the more spin it needs. You are easily meeting the minimum spin requirement for a 45-grain bullet, so what's the problem? Too much spin.
When you have too much spin for a conventional jacketed bullet design, the rate at which its spin is accelerated becomes too great for the friction between the jacket and the core to stand up to. As a result, the lead core starts to slip inside the jacket and never comes up to the full rate of spin of the jacket. This is called "core stripping". The slipping core also becomes deformed by slipping over the rifling marks mirrored on the inside of the jacket, acting sort of like encountering speed bumps at high speed. This deformation puts the center of gravity of the bullet out of line with the bore axis, so it spins around or orbits the bore axis. Like spinning a weight on a string around your head, when the barrel lets go of the bullet jacket at the muzzle, the bullet is not only moving forward but is also flung radially away from the bore line (the line extending the bore axis beyond the muzzle gives you) just like letting go of the string with the spinning weight flings the weight tangentially away from its original circle of spin.
Which direction a core-stripped bullet will take is random as they don't all strip at the exact same position in the barrel. Additionally, since the slower spinning core is more massive than the bullet jacket, via the "speed bumps" it will slow down the rate of spin of the jacket after it exits the muzzle, and the jacket will, to a lesser degree, speed up the core, but the final equilibrated spin rate of the two can be less than the minimum required spin for stability of the bullet.
If the core has stripped but the equilibrated rate of spin beyond the muzzle is not too slow for the bullet, the result is just a very wide group because the radial flinging causes the bullet to drift away from the nominal center of impact in a random direction. If the net spin is too slow for the bullet, you will also get keyholing on the paper. In some cases, especially with thinner bullet jackets, you also get disintegration of the bullet in mid-flight, causing a gray mist to appear between the shooter and the target and for no corresponding hole to appear in the target.
There are two things you can try. One is to go to something more like an 80-grain bullet to reduce angular acceleration and the resulting spin rate to something that will be appropriate for that bullet length. The other is to try solid copper bullets. Solid copper cannot strip and is too strong to disintegrate. However, spin will still fling a bullet radially if it has any degree of imperfect mass distribution or misalignment in the bore, and excessive spin will fling it more, so accuracy will likely depend on loading for minimum cartridge runout, which can require some special tools.
Yes, the bullet is likely too light and is going too fast for that rifling pitch or twist. A 14" pitch is much more appropriate for most bullets in that weight range. Bullets have to have a minimum amount of spin to be stable, and the longer the bullet and the lower its density, the more spin it needs. You are easily meeting the minimum spin requirement for a 45-grain bullet, so what's the problem? Too much spin.
When you have too much spin for a conventional jacketed bullet design, the rate at which its spin is accelerated becomes too great for the friction between the jacket and the core to stand up to. As a result, the lead core starts to slip inside the jacket and never comes up to the full rate of spin of the jacket. This is called "core stripping". The slipping core also becomes deformed by slipping over the rifling marks mirrored on the inside of the jacket, acting sort of like encountering speed bumps at high speed. This deformation puts the center of gravity of the bullet out of line with the bore axis, so it spins around or orbits the bore axis. Like spinning a weight on a string around your head, when the barrel lets go of the bullet jacket at the muzzle, the bullet is not only moving forward but is also flung radially away from the bore line (the line extending the bore axis beyond the muzzle gives you) just like letting go of the string with the spinning weight flings the weight tangentially away from its original circle of spin.
Which direction a core-stripped bullet will take is random as they don't all strip at the exact same position in the barrel. Additionally, since the slower spinning core is more massive than the bullet jacket, via the "speed bumps" it will slow down the rate of spin of the jacket after it exits the muzzle, and the jacket will, to a lesser degree, speed up the core, but the final equilibrated spin rate of the two can be less than the minimum required spin for stability of the bullet.
If the core has stripped but the equilibrated rate of spin beyond the muzzle is not too slow for the bullet, the result is just a very wide group because the radial flinging causes the bullet to drift away from the nominal center of impact in a random direction. If the net spin is too slow for the bullet, you will also get keyholing on the paper. In some cases, especially with thinner bullet jackets, you also get disintegration of the bullet in mid-flight, causing a gray mist to appear between the shooter and the target and for no corresponding hole to appear in the target.
There are two things you can try. One is to go to something more like an 80-grain bullet to reduce angular acceleration and the resulting spin rate to something that will be appropriate for that bullet length. The other is to try solid copper bullets. Solid copper cannot strip and is too strong to disintegrate. However, spin will still fling a bullet radially if it has any degree of imperfect mass distribution or misalignment in the bore, and excessive spin will fling it more, so accuracy will likely depend on loading for minimum cartridge runout, which can require some special tools.
Thank you so much. I kind of figured that was what was going on. I’m using the 45’s for fire forming and will be reloading them in a heavy bullet for deer. Yes I know it’s pretty small for deer but I’ve killed numerous deer with a standard 22-250 55gr. Probably going to reload to an 80gr.
"...couldn’t get it to group..." Doesn't matter when you're forming brass. However, a 45 grain bullet probably won't stabilize with that twist anyway. Plus if that's regular factory .22-250 ammo it'll be under a swarm of assorted pressures while blowing out the shoulders to AI dimensions.
Any issues with the 45 grain ammo brass forming to AI dimensions? That's what's important.
"...22-250 works for deer..." Make sure it's legal for deer where you are. Lotta jurisdictions do not allow .22 CF for deer.
Any issues with the 45 grain ammo brass forming to AI dimensions? That's what's important.
"...22-250 works for deer..." Make sure it's legal for deer where you are. Lotta jurisdictions do not allow .22 CF for deer.
603Country
New member
If the OP isn’t keeping that bullet on a 2 foot by 2 foot target, i’m thinking that the bullet is coming to pieces at that twist and velocity. I’d try a tougher bullet, as Unclenick suggested.